The necessity and desirability of separating blood samples into their respective component parts, for example the cellular components and serum, for test purposes and other medical applications has long been recognized. For example, before a transfusion can be given, the recipient's serum must be tested for the presence of antibodies which would react with antigens present on the donor's red blood cells. It has been estimated that this and similar antibody detection procedures, requiring the washing of red blood cells prior to the addition of Coombs serum, is performed in the U.S. about 250 million times each year. These antibody detection tests require combining donor cells with recipient's serum followed by the separation and isolation of the donor's red blood cells from the recipient's serum. It is well known that such a separation can be effected by centrifugation whereby the red blood cells are forced under increased gravitational forces to the bottom of a centrifuge test tube thereby displacing serum and other less dense components to higher levels. In those operations requiring merely the red blood cell layer, typically the serum portion is decanted and the red blood cells are resuspended in a wash solution. Generally, this solution is a salt based solution. Resuspension of cells is generally accomplished by physical agitation so that any serum which may have been trapped in intracellular spaces between the cells upon centrifugation is similarly resuspended into the solution. The solution containing the newly suspended red blood cells is then typically recentrifuged in order to repack the red blood cells together at the bottom of the tube and the supernate with the contaminating serum is again decanted. This operation of centrifugation and resuspension is generally repeated three times in order to maximize the washing of the red blood cells and remove serum which contains gamma globulin and complement components which would interfere with the Coombs Test yet still retain as many cells as possible. Although the standard recovery system results in a relatively clean population of red blood cells with minimal contamination by other elements present in the blood, there generally is a large loss of red blood cells of between 20 and 30 percent because of the numerous physical operations performed upon the red blood cells. Further, due to the nature of the physical operations required, automated procedures are difficult to institute and require complex, cumbersome, and expensive equipment. In addition, the standard recovery systems require an average of 5 to 6 minutes per 3 wash cycles of the blood sample which puts an increased load upon personnel and equipment resources when large numbers of samples must be handled.
Although there are many types of separation devices available, typically, they are intended to facilitate recovery of the mother solution portion of the suspension and none is intended to solve the aforementioned problems addressed by the present invention.
U.S. Pat. No. 3,932,277 to McDermott et al., directed to the separation of blood fractions, describes a system of tubes, one insertable into the other, whereby one tube inserts a barrier to separate the serum from the red blood cells after centrifuging in an attempt to prevent the mixing of the cells and the serum during decantation of the serum supernatant. During the insertion of the inner tube whereby the barrier is placed between the aforementioned portions, it is possible to have the serum filtered as it passes into the interior of the inner tube. Thus, this invention is directed towards the recovery of serum and requires great care in the placement of the barrier at the surface of the compacted red blood cell portion so as to avoid inadvertant mixing at that interface. Once in place, the barrier will prevent the removal of the red blood cells upon decantation of the serum. Thus, the barrier defeats a technician interested in working with the red blood cell layer from obtaining that cell layer.
U.S. Pat. No. 3,799,342 to Greenspan is similar to U.S. Pat. No. 3,932,277 to McDermott in that it also seeks to place a barrier between the red blood cell layer and the upper serum layer to facilitate removal of the serum and permanent retention of the red blood cells within the centrifugation container. As with the teachings of McDermott, the barrier is to be placed after centrifugation and thus also fails to aid in solving the problems to which the present invention is directed.
U.S. Pat. No. 4,035,294 to Landers et al. is similarly directed towards the collection, filtration and removal of the supernate following centrifugation. Landers et al. teach the insertion of an inner tube having a filter mounted at the bottom whereby, with the application of force to the inner tube upon insertion, the supernate is filtered through the members and is removably collected in the inner tube. As with the previously described references, the disclosure of Landers et al. teaches an improved method in the filtration and handling of liquid supernate materials and fails to supply needed apparatus and methodology for a superior handling of the separated particles from the solution, an object of the present invention.
U.S. Pat. No. 4,244,694 to Farina et al. describes the use of a reactor/separator device for use in automated solid phase immunoassays. The described device employs a water impermeable disc capable of supporting immunoabsorbents, immobilized antisera, ion exchange resins and other similar materials for reaction with reagents added to the inner tube upon centrifugation. Following the desired reaction, additional centrifugal forces are applied in order to force the aqueous phase through the filter making it water permeable thus permitting separation of desired components. Farina's invention provides a device wherein centrifugal force is employed for the mixing, transferance and separation of reactants in a reactor cavity separated from the collection chamber by a water impermeable disc. Such a device fails to solve the problems enumerated above, specifically those related to the collection and washing of particles suspended in a solution where a minimum of steps and a maximization of economy is desired.
Although the collection of the red blood cell component from a blood sample has been described, it is to be understood that this was by way of illustration and that the prior art procedures described as well as the present invention are equally applicable to the separation of particles in general from a mother solution by application of gravitational, electrical or magnetic forces.
It is an object of the present invention to permit the rapid separation of particles from a solution in a "one step" operation. It is another objective that during separation of the particles from the solution containing the particles, the particles are washed so as to remove any nonspecific serum coating and to dilute any solute drag. It is yet another objective that the original containing solution be separately maintained from the resulting particle concentration to permit the removal of the original mother solution in order to reduce contamination. It is still another objective of the present invention that these objectives be accomplished in a simple system capable of economical production and employable within simple, inexpensive centrifuges commonly available. It is still yet another objective that the apparatus and methodology of the present invention be capable of replacing expensive automated cell washers presently available. It is a further objective of the present invention to not only provide methodology whereby the objectives may be accomplished but also devices cabable of meeting the desired objectives. These and other objectives will readily become apparent to those skilled in the art in the light of the teachings herein set forth.